How to fix a sticking black tank valve


By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter he received from a reader while he was serving as’s technical editor.

Dear Chris,
Pulling the black water handle on my 2012 Entegra is getting more difficult compared to the gray water side. Is there any way to ease this or prevent it from getting even more difficult? —Ed

Dear Ed,
This is a common issue that black valves have over time and with repeated use. Lubrication wears off and material can get trapped in the track for the knife valve.

The best way to fix this for the long haul is to service the valve. The valve manufacturers like Valterra make seal replacement kits that are inexpensive and pretty easy to change. Once the tank is emptied, rinsed, and has been left open for 24 hours to “dry” out, you can go ahead and begin the job.

All you will need is a wrench, the kit, and a good valve grease. Dow-Corning 111 is recommended. Remove the four bolts from the valve head, and while lightly prying the pipes apart, remove the valve from the two flanges. There will be a rubber seal on each of the flanges. Remove those, taking note of how they seat in the flange.

Thoroughly clean the valve using a brush, cleaner (like Spray Nine) and copious amounts of water. Look for any damage on the valve that might indicate it needs replacement. Once dry, apply the Dow-Corning 111 to the blade of the valve on both sides and operate the valve until it moves smoothly. Install the new seals that come in the kit onto the flange and coat them with the Dow-Corning 111 to help hold the seals on the flange. Then, while prying the pipes apart, slide in the valve and align the bolt holes and install the new bolts that come with the kit.

While there are other “homebrew” ways of treating sticky valves that may work for a little while, the repair I noted here will make the valve operate like new for a long time.

As a side note, you may not “need” to replace the seals; however, any kink in the seal can result in a leak. For the minimal cost, I think it’s better to go ahead and change the seals. You can also replace the entire valve for a bit more money, but I would still apply the Dow-Corning 111 to the new valve before installing it.


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Al F
1 year ago

Would you explain the difference between Dow-Corning 111 and the common plumbers silicone you can buy in the hardware store? Both seem to be food grade silicone grease lubricant. I have used the hardware store one for several years and it seems to work just fine. BTW the hardware store variety is $3-$4 and the Dow-Corning 111 is $20 at Amazon.

1 year ago

The OEM version of our Tank Valves had flat blades that slid in the track. Once the edge grabbed the rubber seal, it was all over. I had to pull the valves out and either replace the valves all together, or at least replace the existing seals. I chose the former and purchased Valterro valves. Right away, I noticed a difference in the design. The Valterro valves had tappered or knife blade edges. That prevents the valve from grabbing and damaging the valve seals. Instead, they slip right on by.

On the subject of “oil” on the blades (regardless of method getting it there), it would seem a bad idea. Not so much from your point of correcting the problem but from the Landowners respect. Oil is not good in a septic system. And it’s also not good in a City sanitation system (we’re talking copious amounts here. Not a simple quick spray). I preferred to use plumbers grease which so far has worked pretty well.

And prior to installing the new valves, I also pulled the handle out of the sleeve and input a lightweight oil. It’s been about a year now and all still works well.

Jack Gregory
1 year ago

When trying to re-install the valve and you find the fit too tight, thereby making it really really difficult to get the seals to install properly. Head to the kitchen and re-purpose one of your wife’s Teflon chopping sheets (the really thin ones). Cut it in half and put on each side of the valve, slide the valve and seal in, then carefully remove the Teflon sheet, a little kitchen spray on the sheet makes removal of the sheet easier! DON’T try to sneak the Teflon sheet back into the kitchen, just own up to the theft and promise not to do it again

3 months ago
Reply to  Jack Gregory

I like it! (promise not to do it again.. Hell, that should be my motto)

Dwayne N
1 year ago

I have read a number of online posts where individuals claim using a little cheap vegetable oil can help lubricate the valves. Here is one such post:

“Their solution was to drain the tank and then put a few gallons of water back in. Then flush 2 cups of cooking oil down the toilet. Go back outside and move the valve handle in and out a few times while the oily water is draining. I wouldn’t have believed it, however, ours became silky smooth after the treatment. I now do this on a regular basis, on each 4th dump of the tank. Works great!! No more sticky valves. By the way it works well on the gray tanks also. Hope this helps. If you have sticky blade valve gaskets it just might.”

1 year ago

If the black or gray tank handle is sticky and the valve is not leaking, here’s a quicker way of fixing it: drill a hole one inch above the center of the handle using a 1/8 inch drill bit. Spray silicone lube into the hole using the red extension nozzle. Work the handle back and forth several times while spraying a little more lube. If a lot of gunk comes out of the black tank handle hole, continue giving short bursts of lube while working the handle, until the lube coming out of the hole runs clean. Your handles will work like never before.